If we don't know what an object is, then we don't know what it isn't either. This much is obvious. The people jumping to the conclusion that it _must_ be mundane are making the same mistake as the people who claim the opposite. We simply need better evidence.
Could it be aliens? Technically, I guess. Just like it could technically be craft sent by advanced beings living in the center of a hollow Earth.
It makes sense to start with hypotheses that are actually likely, or at least not terribly unlikely, before going on flights of fancy.
In this case it doesn't. the expensive part was tracking the objects and taking one down, after that it's just recovering and studying the debris. If it's alien, it should be easy to tell.
"Extraordinary claims require extraordinary evidence" - in other words, this speculation can be dismissed without additional proof
What Loeb is pointing at is that in the real world you can't expect extraordinary scientific evidence while refusing to fund the research that could produce such evidence.
I am not claiming that these observations are caused by aliens. I am merely pointing out the inherent contradiction behind statements like "we don't know what this is, but [we sure know] it is not aliens".
Logic doesn't work that way.
We don't know all of the things it isn't. We can know many individual things it's not. I know that none of the UFOs in the news are my left shoe.
Do I believe aliens are visiting Earth? Frankly, I do not. But I can't dismiss it outright either, because we don't know what we don't know.